Single particle resuspension experiments in turbulent channel flows

The resuspension of spherical single particles from a hydraulically smooth wall into a turbulent flow is studied. Special attention is given to the particle diameter, the material composition, the critical friction velocity and the inceptive motion of the resuspending particles. The experiments were performed in an air-driven small-scale test facility. The particles on the channel floor were detected and classified by means of an optical microscope combined with a digital camera. Furthermore, the turbulent flow field was recorded using a conventional Particle Image Velocimetry (PIV) system. A statistical sufficient monolayer of spherical particles was generated on the channel floor by dispersing the particles into the flow during a pure deposition regime. Afterwards, particle resuspension was induced by the stepwise increase of the fluid velocity. The resuspension was quantified by the fraction of resuspended particles against the friction velocity for a diameter range between 3 and 45 µm. It was found that particles begin to resuspend when a critical friction velocity is exceeded. A decreasing tendency between the particle diameter and the critical friction velocity was found for particles in the present size range and the results are in good consistency to other investigations.